To study comprehensively a primary system of communication in a large-brained mammalian species other than man. It is proposed that the various talents of an interdisciplinary group, largely assembled already, be brought to bear on this problem. The objective has been narrowed to focus upon acoustic communication; the Atlantic bottlenosed dolphin is proposed as the subject of choice as: (1) It lives primarily in an acoustic world. (2) It produces two types of sound, one of which, the whistle, is more subject to quantification than most mammalian sounds. It is planned to study the narrow-band whistle emission of the dolphin in relation to the behavior of the animal and especially to make systematic correlations between these emissions and the physiological condition of the individual (such as age, sex, amount of stress, social encounters, etc.). Natural and synthetic whistles will both be used in defining these factors.